It is desirable to sense and inform the driver when automotive brake pads need to be replaced. Known electronic brake wear sensors have a resistor circuit sensor that is clipped to the inner brake pad. As the pad is abraded away by the rotor, the sensor is also abraded away, changing its resistance. A pigtail harness is connected to the sensor which is wired to a sensing module in the vehicle.
There are several problems with the known approach. The multiple wire harnesses required and the additional sensing module makes this an expensive solution. Routing of the harnesses through the vehicle suspension and the wheel/steering knuckle area is very challenging and prone to road debris abuse. Additionally, the wear sensor has to be replaced each time the pads are replaced, which can be expensive.
While employing electronic sensors to detect brake pad wear, it is important to consider that the brake pad and brake caliper area can reach temperatures in excess of 300 degrees C., which many electronic sensors cannot withstand.
From a cost and implementation standpoint, it is desirable to not use any wire harness and to try to utilize existing product already on the vehicle to reduce the cost of transporting the pad wear information to the driver display. It is also desirable that it not be necessary to replace the brake pad wear sensor with the brake pads when they are replaced. It is also desirable that the brake pad wear sensor provides diagnostic (e.g., heartbeat) capabilities, and the sensor must be capable of withstanding the extreme temperatures seen during braking.